An inkjet printer of an ink circulation type is known. The inkjet printer of the ink circulation type performs printing by ejecting an ink from an inkjet head while circulating the ink.
Patent Literature 1 listed below discloses an inkjet printer which circulates an ink by using a pressure difference obtained by causing an air pump to increase a pressure in a positive pressurization tank provided upstream of an inkjet head in an ink circulation path and decrease a pressure in a negative pressurization tank provided downstream of the inkjet head in the ink circulation path.
The inkjet printer of this type sends air from the negative pressurization tank to the positive pressurization tank at the start of ink circulation by driving the air pump to generate preset pressures respectively in the positive pressurization tank and the negative pressurization tank for the ink circulation. Thereafter, the air pump is driven depending on pressure fluctuation in the positive pressurization tank and the negative pressurization tank to maintain the pressures in the positive pressurization tank and the negative pressurization tank.
In the maintaining of the pressures after the generation of the preset pressures, the drive rate (drive duty ratio) of the air pump is set lower than that in the generation of the preset pressures. Performing such control achieves fine pressure adjustment with the pressure fluctuation being suppressed.